BuzzFeed, from 26 employees, to 150

BuzzFeed President Jon Steinberg says developing effective social advertising will become more important as Web traffic increasingly goes mobile. The right column of a website that is typically reserved for banner ads disappears on a mobile device, so putting ads in online conversations becomes crucial, he says. "Social advertising is going to eat display advertising," he says, adding that BuzzFeed's ads cost roughly the same as a premium display ad.

BuzzFeed says it is on track to triple its revenue this year, and that its staff has grown to around 150 from 26 at the start of last year. Much of the staff growth has been powered by $15.5 million in third-round financing led by New Enterprise Associates in January. But Mr. Peretti says ad revenue recently began to finance more growth than the venture funding. Traffic doubled to 10 million unique visitors in August from a year earlier. Advertisers include Toyota Motor Corp., General Electric Co. and PepsiCo Inc.

BuzzFeed also has been strengthening its ties to Facebook. In September, BuzzFeed hired former Facebook communication designer Jeff Greenspan to be creative chief. The company also acquired Kingfish Labs, a start-up that gathers Facebook data. And when Facebook wanted to try a new ad format, it tapped BuzzFeed as part of a select group to test it, Facebook says.

"We are very complementary companies," Mr. Peretti says. "They own the railroad tracks, we drive the trains."